Transformer ventilator



Feb. 7, 1939. R. R. PITTMAN ET AL TRANSFORMER VENTILATOR Filed Sept. 6, 1938 2 l 4 W llwmzzwlll 2 s 2 Z M AA WW H/ P INVEN 0R5 @411 Vital W 14 MM surface of the tank cover.

Patented F eb. 7, 1939 UNITED STATES TRAN SFOBMER VENTILATOR Ralph n. Pittman in cal-mu n. Walsh, Pine Bluff, Ark.

Application September 6, 1938, Serial No. 228,593

3 Claims.

This invention relates to electric transformers, particularly to a venting or breathing organization for use with transformers of the distribution type, in which the insulating and cooling medium does not entirely fill the transformer tank.

Heretofore considerable difilculty has been experienced with apparatus of this type, due to com densation of water vapor within the unfilled portion of the tank, and particularly on the inner Such condensation of moisture, which occurs in response to a temperature change sufficiently great to cool the adjacent water vapor to a temperature at or below its dew-point, and which is often caused by rain impinging upon the cover, not only causes rusting of the inner surface of the cover, but also greatly reduces the insulating quality or dielectric strength of the cooling liquid.

Present available distribution transformers are in general provided with no means for preventing the moisture condensation mentioned above, and it is a principal object of the present invention to provide means for preventing or greatly inhibiting such condensation.

More specifically, an object of the present invention is the provision of means for preventing moisture condensation within the unfilled portion of a distribution transformer by first utilizing the inherent losses of the transformer for heating air entering the unfilled portion, and subsequently causing the so-heated air to pass or sweep over the inner surface of the transformer cover en route to the atmosphere.

With these and other objects in view which will appear as the description proceeds, our invention resides in the novel arrangement and construction of the ventilating system, in combination with the elements of a distribution transformer, and the scope of the invention is set forth in the appended claims.

In the drawing: Fig. 1 illustrates in section a distribution transformer embodying our novel ventilating system; Fig. 2 is a fragmentary sectional view of the oil sampling valve in combination with the air inlet of the ventilator; Fig. 3 is a plan view of the transformer of Fig. 1 in which a portion of the cover is shown removed; and Fig. 4 illustrates in section a reversible plug for use with the oil sampling valve and air inlet.

The arrangement of the air inlet and oil sampling valve illustrated herein has been previously described in our copending application Serial No. 210,196, filed May 26, 1938, but it may be noted that the ventilating arrangement described herein, depending as it does upon passage of heated air over the inner surface of the transformer cover, has not been heretofore disclosed in the above application, and the claims of the present application are substantially limited to a construction which employs the above described method for preventing the undesired condensation.

Referring more in detail to the drawing, a transformer tank I0 is provided with a cover II, a gasket 18 being employed to assure a tight seal between these elements. A core-and-coils assembly I2 is contained by the tank II, and is electrically connected through the conductors l3 and M to the entrance bushings l5 and [6 respectively. A non-aqueous cooling or insulating material 21, such as oil, partially fills'the tank ll to the oil level 23, the winding assembly I 2 being submerged in the oil 21 in accordance with common practice. Preferably, the space 35, which is above the oil level 23, and within the tank 10, is tightly sealed for preventing entrance of atmosphere at any points other than those forming a part of the ventilating system now to be described.

A hollow tubular conduit 20, having a substantial portion thereof extending upwardly within the tank Ill, and in intimate association with the oil 2|, terminates at its upper end in the space 35. The upper end portion of the conduit 20 is preferably extended circumferentially in a horizontal plane adjacent a substantial portion of the periphery of the cover H, and the opening connecting the hollow of the conduit with the space 35 is v in the form of a slot 19, adjacent the inner surface of the cover. The lower end of the conduit 20 is open to the atmosphere, the manner of opening being described in detail later. A vent or breather II, providing a passageway between the space 35 and the atmosphere, is mounted on the cover H at a point remote from all portions of the slot IS. The vent I1 is preferably of sucha construction that air currents passing over or impinging upon the vent will tend to withdraw air from the space 35, the construction of such vents being well known in the ventilating art.

With such an arrangement in mind, it will be apparent that atmospheric water vapor, whether saturated or unsaturated, entering the space 35, will do so only through the conduit 20, and will be expelled from the space 35 to the atmosphere through the vent H. The water vapor in its passage upwardly through the conduit 20 to the space 35 is heated by the electrical losses inherent in the winding assembly, with the result that the temperature of the water vapor is raised, thereby causing it to reach a condition in which it is much farther removed from the dew-point than if it were not so heated. Obviously the heating of the water vapor per se is of great assistance in inhibiting its condensation inasmuch as the extent of cooling in order to reach dew-point has been greatly increased.

While the heating of the entering air from the losses of the transformer is in itself of considerable benefit in attaining the objects of the present invention, a further benefit results from the arrangement of the upper opening N of the conduit 20 with respect to the vent H, as will now be pointed out.

A very pronounced chimney effect results from the passage of the heated atmospheric water vapor from the inlet at the lower end of the conduit 20 outward through the vent H. The arrangement is such that the water vapor in its passage between the points described in the order named, and after being heated during its passage through the upwardly extending portion of the conduit 20, is caused to sweep across the inner surface of the cover H as it moves from the slot l9 to the vent H. The accomplishment of such a movement not only inhibits condensation but should any condensation have formed due to unusually extreme temperature change of the cover H, such condensation will be carried out of the vent I! rather than forming in continuously growing drops to eventually fall into the oil. The latter condition is that found in present types of distribution transformers. It may be noted that the several objects of our invention are accomplished by a construction in which the two principles cooperate to achieve the desired results.

Electric distribution engineers have long been aware of the desirability of an inexpensive and effective means of reducing or preventing moisture condensation within transformer tanks, and as late as 1938 some companies report spraying the inside surface of transformer tanks to prevent iron rust falling into the oil. It is apparent that resort to schemes of this nature fail as a complete solution to the problem, which in its essence is one of inhibiting condensation.

We will now explain the manner for terminating the lower or inlet end of the conduit 20. Referring in detail to Fig. 2, a valve body 26 is secured, by means of the threaded fitting 25, to the end of the conduit portion 20, in such a manner that the hollow of the conduit portion 20 is in alignment with an opening 21 through the inner portion of the valve body 26, and the outer portion of the valve body is provided with an internally threaded recess, into which is screwed the plug 30, the opening 3| through the latter being coaxial with the opening 21 of the valve body 26. A laterally extending oil passageway 28 connects the oil 2| with the internal threaded recess of the valve body 26, but under normal conditions the outward passage of the oil 2| is prevented by the fiber washer 29, which normally tightly closes the outer end of the opening 28. It will be apparent that oil will fiow through the passageway 28 to the opening 3! if the plug 30 is rotated in a direction to remove it.

Since it is desirable to transport the transformer filled with oil, we provide the reversible plug shown in Fig. 4, which is threaded at each end to fit the internally threaded portion 32 of the plug 30. In shipment, that end of the plug having'no opening therein is screwed into the portion 32,'which efiectively prevents escape of oil through the conduit 20. After the transformer is permanently installed in position, the plug 33 is removed, and reinserted with the opening 34 in communication with the opening 3| of the plug 30. An opening 24 extends laterally through the plug 33, so as to intersect the opening 34, thus forming a continuous passageway under normal conditions from the opening 24 through the fittings and conduit to the opening l9 at the upper end of the transformer.

While we have herein .illustrated and described in detail a specific embodiment of our invention it will be apparent to those skilled in this art that other constructions may be used without departing from the principles exemplified and it is to be understood that our invention is to be limited only as is necessitated by the prior art and the appended claims.

What we claim is new, and desire to secure by Letters Patent of the United States is:

1. In electric apparatus which includes a container, a cover for the container, a cooling liquid partially filling the container, and an electrical device subject to losses expressed as heat in contact with said liquid, an upwardly extending conduit forming a continuous passageway connecting the medium surrounding the apparatus with the unfilled portion of the container, a substantial portion of said conduit being positioned within said container and in intimate relation with said cooling medium whereby water vapor passing upwardly through said conduit is heated, a vent in said cover relatively remote from the upper end of said conduit, and a valve at the lower end of said conduit, said valve being interposed between the latter and said cooling liquid.

2. In a transformer having a tank, a cover for the tank, a non-aqueous cooling liquid partially filling the tank, and a winding subject to losses expressed as heat, said winding being intimately associated with said cooling liquid, a conduit connecting the unfilled portion of the tank with the atmosphere, said conduit extending continuously downward from the opening to said unfilled portion of the opening to the atmosphere, a substantial portion of the conduit being intimately associated with said cooling liquid whereby air entering the unfilled portion' of the tank is heated in passing upwardly through said conduit, a vent in said cover in communication with the atmosphere, said vent being so related to the open upper end of said conduit that the heated air passing upwardly therefrom impinges upon the inner surface of said cover, a valve associated with the lower end of said conduit, said valve being interposed between the latter and said liquid, and means externally of said tank for operating said valve.

3. In a transformer having a tank, a cover for the tank, a non-aqueous cooling liquid partially filling the tank, and a winding subject to losses expressed as heat, said winding being intimately associated with said cooling liquid, a conduit connecting the unfilled portion of the tank with the atmosphere, said conduit extending continuously downward from the opening to said unfilled portion to the opening to the atmosphere, a substantial portion of the conduit being intimately associated with said cooling liquid whereby air entering the unfilled portion of the tank is heated in passing upwardly through said con duit, a vent connecting the unfilled portion of the tank with the atmosphere, said vent being so related to the open upper end of said conduit that the heated air passing upwardly therefrom moves in a path along the inner surface of said cover, and valve means associated with the lower open end of said conduit for withdrawing said liquid from the container.

RALPH R. PI'I'I'MAN. CARROLL H. WALSH. 

